.ir-arriba {
  padding: 5px;
  display: inline-block;
  background-color: rgba(0, 0, 0, 0.6);
  color: #fff;
  position: fixed;
  font-size: 24px;
  bottom: 10px;
  right: 10px;
  display: none;
  cursor: pointer;
  border-radius: 5px; /** 50px para que sea redondo **/
  font-size: 2rem;
  z-index: 999999;
}